Abstract
The direct effects and the intracellular pathways of rCGRP were investigated on smooth muscle cells (SMC) isolated by enzymatic digestion from the circular and longitudinal layers of guinea-pig ileum. In circular SMC, rCGRP inhibited CCK8-induced contraction in a concentration-dependent manner (Cmax = 100 microM and EC50 = 0.7 +/- 0.4 nM). Preincubation of SMC with 1 microM Rp-cAMPs, a cAMP antagonist, abolished the relaxing effect of rCGRP; moreover, preincubation of SMC with 100 microM L-NAME, an inhibitor of NOS, inhibited the relaxing effect of rCGRP, hCGRP(8-37), a selective antagonist of rCGRP receptors, inhibited the rCGRP-induced relaxation in a concentration dependent manner whereas the vasoactive intestinal polypeptide (VIP) antagonist had no significant effect. In longitudinal SMC, rCGRP-induced relaxation was abolished by Rp-cAMPs, whereas L-NAME had no effect. In conclusion, rCGRP triggers different intracellular pathways to induce relaxation of circular or longitudinal intestinal SMC; cAMP is involved in cells from both layers while nitric oxide (NO) is involved only in relaxation of circular SMC.
MeSH terms
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Animals
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Arginine / pharmacology
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Calcitonin Gene-Related Peptide / pharmacology*
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Calcitonin Gene-Related Peptide Receptor Antagonists
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Cyclic AMP / analogs & derivatives
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Cyclic AMP / antagonists & inhibitors
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Cyclic AMP / metabolism*
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Cyclic AMP / pharmacology
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Guinea Pigs
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Ileum / drug effects*
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Ileum / physiology
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In Vitro Techniques
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Muscle Contraction / drug effects
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Muscle Relaxation / drug effects*
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Muscle, Smooth / drug effects*
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Muscle, Smooth / physiology
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NG-Nitroarginine Methyl Ester / pharmacology
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Nitric Oxide / antagonists & inhibitors
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Nitric Oxide / metabolism*
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Peptide Fragments / pharmacology
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Recombinant Proteins / pharmacology
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Sincalide / antagonists & inhibitors
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Sincalide / pharmacology
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Thionucleotides / pharmacology
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Vasoactive Intestinal Peptide / antagonists & inhibitors
Substances
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Calcitonin Gene-Related Peptide Receptor Antagonists
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Peptide Fragments
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Recombinant Proteins
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Thionucleotides
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calcitonin gene-related peptide (8-37)
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adenosine-3',5'-cyclic phosphorothioate
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Nitric Oxide
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Vasoactive Intestinal Peptide
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Arginine
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Cyclic AMP
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Calcitonin Gene-Related Peptide
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Sincalide
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NG-Nitroarginine Methyl Ester